Coal is the major source of fossil fuel resource in the United States. It has been estimated that the United States has enough coal to last about 600 years at the present rate of consumption, whereas the supply of petroleum is expected to last for only another 25 to 50 years.
The automotive industry is a large consumer of petroleum. If this industry is to continue after the world's supply of petroleum has been exhausted, it must convert to an alternate source of energy. One potential source of energy is coal, fired directly as a solid fuel or mixed with oil or gasoline and fired as a slurry.
While the use of coal could result in easing or ameliorating the problem, it is not without problems. All coals contain excessive amounts of sulfur and ash which must be reduced to low levels in order to prevent excessive corrosion and erosion of the engines and pollution of the atmosphere.
Therefore, one of the first problems to overcome in the utilization of coal as an alternate automotive fuel, and as a substitute for petroleum as source of energy in other applications, is to produce a coal having the desired purity.
The present invention comprises a method of treating a solid carboanceous material comprising essentially lignite or bituminous or subbituminous coal to provide therefrom finely dispersed particles that are substantially free of ash and sulfur. The particles have a variety of uses. For example, they may be dried to provide a powdered fuel usable in internal and external combustion engines, furnaces, or other combustion devices; they may be liquefied, or else mixed with carbonaceous liquid, to provide a liquid fuel that is similarly usable; or they may be compressed, either with or without a binder material, into solid pieces for use as briquets for burning in furnaces and other combustion devices or as electrodes.